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Abstract

Species of the genusShewanellaare widespread in nature in various
habitats, however, little is known about phages affectingShewanellasp.
Here, we report the isolation of phages from diverse freshwater
environments that infect and lyse strains ofShewanella oneidensisand
otherShewanellasp. Sequence analysis and microscopic imaging strongly
indicate that these phages form a so far unclassified genus, now
namedShewanellaphage Thanatos, which can be positioned within the
subfamily
ofTevenvirinae(Duplodnaviria;Heunggongvirae;Uroviricota;Caudoviricetes;C
audovirales;Myoviridae;Tevenvirinae). We characterized one member of
this group in more detail usingS. oneidensisMR-1 as a
host.Shewanellaphage Thanatos-1 possesses a prolate icosahedral capsule
of about 110 nm in height and 70 nm in width and a tail of about 95 nm
in length. The dsDNA genome exhibits a GC content of about 34.5%, has a
size of 160.6 kbp and encodes about 206 proteins (92 with an annotated
putative function) and two tRNAs. Out of those 206, MS analyses
identified about 155 phage proteins in PEG-precipitated samples of
infected cells. Phage attachment likely requires the outer
lipopolysaccharide ofS. oneidensis, narrowing the phage's host range.
Under the applied conditions, about 20 novel phage particles per cell
were produced after a latent period of approximately 40 min, which are
stable at a pH range from 4 to 12 and resist temperatures up to 55
degrees C for at least 24 h. Addition of Thanatos toS. oneidensisresults
in partial dissolution of established biofilms, however, early exposure
of planktonic cells to Thanatos significantly enhances biofilm
formation. Taken together, we identified a novel genus of Myophages
affectingS. oneidensiscommunities in different ways.